#!/usr/bin/env python


# RSA decode 
def unmakedes(x,d=11,n=4097): return pow(x,d,n)
# Lots of scrambling
def undoit(x): return ((7-x)*3+5)%8
def undotooit(x): return ((13-x)*5)%8

#(defun un-permute-it (x) 
#	(setf new 0)
#	(dotimes (temp 8)
#		(if (= (mod x 2) 1)
#			(setf new (+ new (expt 2 (un-do-it temp)))))
#		(setf x (/ (- x (mod x 2)) 2)))
#	(setf x new))
#(defun un-waymute-it (x)
#	(setf new 0)
#	(dotimes (temp 8)
#		(if (= (mod x 2) 1)
#			(setf new (+ new (expt 2 (un-do-it-too temp))))
#			())
#		(setf x (/ (- x (mod x 2)) 2)))
#	(setf x new))

def unpermuteit(x): return sum(2**undoit(i) for i in filter(lambda y:(x>>y)&1==1,range(8)))
def unwaymuteit(x): return sum(2**undotooit(i) for i in filter(lambda y:(x>>y)&1==1,range(8)))

#(defun un-happenin (x1 y1 z1)
#	(setf this-num (un-make-des (+ x1 (* (mode y1 little) lot)))
#		that-num (un-make-des (+ (* z1 little) (/(- y1 (mod y1 little)) little))))
#	(setf	temp1 (mod this-num lot)
#		temp2 (+ (/ (- this-num temp1) lot) (* (mod that-num little) little))
#		temp3 (/ (- that-num (mod that-num little)) little)))

#Group 3 8-bit chars into 2 12 bit numbers, RSA-decrypt them and split result back into 3 numbers
def unhappenin (cell):
	(x1,y1,z1)=cell
	d1=unmakedes(((y1&0xf)<<8)+x1)
	d2=unmakedes((z1<<4)+(y1>>4))
	return (d1&0xff,((d2&0xf)<<4)+(d1>>8),d2>>4)

# Main decryption function
# Read 3-byte cells, permutate mid character, RSA-decrypt it and permutate all members of the cell
def unrollthetext(thetext,wend=-1,celllength=3):
	rc=""
	if wend<0: wend=len(thetext)
	numcells=wend/celllength
	for i in range(numcells):
		cell=(ord(thetext[3*i]),unwaymuteit(ord(thetext[3*i+1])),ord(thetext[3*i+2]))
		rc+="%c%c%c" % tuple(map(unpermuteit,unhappenin(cell)))
	return rc


# --- END OF AGRIPPA DECRYPTION ALGORITHS ---

# Read codebitsz bits at position idx from a stream 
def parsestream(arr,idx, codebitsz):
	(offs,idx)=(8-(idx&7),idx//8)
	rc=ord(arr[idx])&((1<<offs)-1)
	(offs,idx)=(codebitsz-offs,idx+1)
	if offs>8:
		rc=rc*256+ord(arr[idx])
		(offs,idx)=(offs-8,idx+1)
	if offs!=0:
		rc=rc*256+ord(arr[idx])
		rc=rc>>(8-offs)	
	return rc

# Classical Lempel-Ziv-Welch decompressor
def LZWDecode(stream):
	(rc,conj,idx,codebitsz)=("","",0,9)
	dict=map(chr,range(256))
	dict.append(chr(0))
	while idx<len(stream)*8:
		e=parsestream(stream,idx,codebitsz)
		idx+=codebitsz
		# 0x100 is end of stream marker
		if e==0x100: break	
		if e==len(dict):
			dict.append(conj+conj[0])
		elif len(conj)>0:
			dict.append(conj+dict[e][0])
		rc+=dict[e]
		conj=dict[e]
		if codebitsz<12 and len(dict)==1<<codebitsz: 
			codebitsz+=1
	return rc

# Main routine
if __name__ == "__main__":
	from sys import argv,exit
	from os.path import exists
	#File name
	fname="Agrippa"
	if len(argv)>1: fname=argv[1]
	if not exists(fname):
		print "Failed to open %s: Please put original (or modified) Agrippa executable to the same folder as %s" % (fname, argv[0])
		print "On Mac OS X Agrippa can be extracted from fd0-agrippa.dmg using following commands:"
		print "\t$ hdiutil attach fd0_agrippa.dmg"
		print "\t$ cp /Volumes/Agrippa\(a\ book\ of\ the\ dead\)/Agrippa ."
		print "\t$ hdiutil detach /Volumes/Agrippa\(a\ book\ of\ the\ dead\)/"
		print "Or pass the path to Agrippa binary as first argument to the script"
		exit(0)
	print "Reading %s..." % fname,
	data=open(fname).read()
	print "%d bytes read" % len(data)
	print "Decompressing LISP binary...",
	decompressed=LZWDecode(data[0x80d1c:])
	print "%d bytes decompressed" % len(decompressed)

	print "\n\n\nAnd now, TheText\n\n:"
	print unrollthetext(decompressed[4875:4875+3306*3]).replace("\r","\n")